This invention relates to a gas bag restraint device.
Known gas bag restraint devices comprise a gas module, which has a gas bag with a gas bag wall which gas bag wall comprises a front wall upon which the occupant to be restrained can impact in the case of restraint, and which front wall has a depression formed by a ring-shaped gas bag wall portion, in that a center portion of the front wall is attached to the module and is prevented from a free, preferably any movement when the gas bag is inflated. Such ring-shaped gas bags have a large impact area that can be presented to an occupant to be restrained, as they are first of all deployed radially towards outside.
The invention provides a gas bag restraint device with a depression and, nevertheless, a large and increased impact area in the region of the depression. This is achieved in a gas bag restraint device which comprises a gas bag module which has a gas bag with a gas bag wall. The gas bag wall comprises a front wall upon which an occupant to be restrained can impact in a case of restraint. The front wall has a depression defined by a ring-shaped gas bag wall portion. The depression is generated in that a center portion of the front wall is attached to the module and is prevented from a free, preferably any movement when the gas bag is inflated. Holding means are provided at the ring-shaped gas bag wall portion that keep parts of the ring-shaped gas bag wall portion contacting each other when the gas bag is inflated in contact with each other in a fully inflated condition of the gas bag, and at least partly close the depression. Despite these holding means, the gas bag can first move outwards during deployment and, in so doing, assume a toroidal shape. However, there is usually obtained a dynamic movement, i.e. the ring-shaped chamber to be filled with gas with the ring-shaped gas bag wall portion defining the depression collapses towards inside, so as to at least partly close the depression. After the first contact of parts of the ring-shaped gas bag wall portion, there occurs in prior art devices a movement radially towards outside, so that the depression is exposed again. In the device proposed, however, the contact is maintained by the holding means when parts of the ring-shaped gas bag wall portion come together, so that the exposed cross-sectional area of the depression at least as seen from the front wall is smaller than in prior art devices. Preferably, the depression is even closed completely.
In accordance with the preferred embodiment, the holding means are disposed at the entrance of the depression, i.e. directly at the transition from the front wall portion facing the occupant and its portion defining the depression (center portion plus ring-shaped gas bag wall portion).
The holding means are usually disposed at opposite parts of the ring-shaped gas bag wall portion and then connect these parts.
The holding means are, for instance, designed as adhesive means or as a hook and eye closure such as VELCRO(copyright).
In accordance with the preferred embodiment, the depression is closed by the holding means such as to form a slot when the gas bag has been inflated.
Another advantage, for instance of the hook and eye closure such as VELCRO(copyright), consists in that the same can be used for fixing the air bag in a folding machine while the gas bag module is assembled.
To ensure the contact of the parts of the gas bag wall, limiting straps are provided adjacent the depression in accordance with the preferred embodiment, which limiting straps limit the depth of the gas bag and define the depth of the depression. As a result, the ring-shaped gas bag wall portion need not effect the limitation in depth and can bulge radially inwards.